Process for stabilization of copper treated oils



Patented May 20, 1941 PROCESS FOR, STABILIZATION OF COPPER TREATED OILS Walter A. Schulze, Bartlesville, Okla", and Graham H. Short, Phillips, Ten, assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Original application November 9,

1938, Serial N0. 239,731. Divided and this application May 28, 1940, Serial No. 337,737

2 Claims.

This invention relates to a new and useful process for treating hydrocarbon oil. More specifically, this invention relates to a process for stabilizing or preventing the deterioration of hydrocarbon oil which has undergone a purifying treatment with reagents containing copper.

This application is a division of our copending application Serial No. 239,731, filed November 9, 1938.

Hydrocarbon oil, particularly petroleum distillates usually contain impurities, including sulfur compounds, which cause the oil to exhibit undesirable properties such as bad odor and gum and color formation. It is customary, therefore, to subject said impure oil to a purifying treatment in order to remove the impurities or to convert them to less objectionable forms, for example, the conversion of mercaptans to disulfides.

The methods of treatment for the removal or conversion of mercaptans make use of various chemical processes, and of these processes, one of the most satisfactory is the process utilizing copper, salts of copper, or solutions containing copper salts.

However, subsequent to treatment with coppercontaining reagents, it has been found that many hydrocarbon oils require further treatment or stabilization. This condition is due to the fact that said unstable oils retain from their contact with copper reagents, extremely small quantities of oil-soluble copper compounds. These traces of copper compounds remaining in the oil are responsible for the marked acceleration of reactions which lead to the formation in said oil of color, gum, resinous deposits and polymers; these deteriorative changes seriously impair such properties of the oil as color, gum content and octane number.

One object of this invention is to effect the removal of traces of copper compounds from hydrocarbon oils.

Another object of this invention is to prevent the deterioration of hydrocarbon oil which has been treated with copper reagents by the removal from said oil of small amounts of retained oil-soluble copper compounds responsible for aforesaid deterioration.

A further object of this invention is the production of hydrocarbon oil of good color and stable with respect to gum formation subsequent to treatment with copper-containing reagents.

A further object of this invention is the treatment of oil which retains traces of copper compounds subsequent to sweetening with copper reagents, to remove said copper from the oil, thereby delaying or preventing deterioration.

Another object; of this invention is to provide a step in the sweetening of hydrocarbon oil with copper reagents whereby the sweetened oil is stabilized against deterioration by the removal therefrom of retained copper salts.

Another object of this invention is the conversion of oil-soluble copper compounds present in hydrocarbon oil as a result of sweetening with copper reagents to oil-insoluble compounds, said conversion resulting in complete separation of the insoluble copper compounds from the oil.

Schulze and Frey in U. S. Patent No. 1,980,555 described a method for stabilizing an oil treated with copper and which exhibited discoloring and/or formation of resinous matter, polymers and oxidation products; that is, a method of stabilizing the oil by bringing it in contact with an alkaline sulphide solution subsequent to treating with the copper reagent.

We have now discovered that copper treated oils may be stabilized by means other than the alkaline sulfide solution referred to above and that these means involve certain improvements and advantages. This discovery is extremely important in that it clearly defines the conditions which must be met to produce stabilized oils. This discovery, likewise makes it possible to divide treating agents into two groups, the first group consisting of those reagents which will effectively remove the hydrocarbon oil-soluble copper compounds and thereby stabilize the oil, and the second group consisting of those reagents which will not remove sufiicient quantities of the copper compounds to stabilize the oil.

We have found that copper mercaptides increase in solubility in the oil with increasing molecular weight of the mercaptans. Copper methyl mercaptide is the most insoluble of all the copper mercaptides and is almost totally insoluble in hydrocarbon oils. Copper ethyl mercaptide, the next number in the series, is a little more soluble, yet its actual solubility figure is extremely low. .Copper butyl mercaptides and amyl mercaptides are much more soluble and their solubilities may be determined in the usual manner of precise measurements.

We have now discovered that hydrocarbon oil containing copper methyl mercaptide, and therefore completely saturated with respect to the substance, does not show any of the undesirable reactions mentioned above as resulting from the catalytic enect of dissolved copper compounds. In other words, we have established that the concentration oi copper from a saturated solution of copper methyl mercaptide in hydrocarbon plete removal of the copper is not eflected by treatment of the oil with caustic soda, carbonate or phosphate solutions, or by the addition to the oil of controlled amounts of ethyl mercaptan.

oil is too low to cause deterioration of the oils. 5 In order to explain more exactly the criterion 0n the other hand, we have found that if the by which the stabilization of copper-containing hydrocarbon is saturated with respect to copper oil is judged, the relative solubilities of the copper ethyl mercaptide, the concentration of copper is compounds encountered may be considered. Just suillcient to cause a'slow depreciation in the The sulfides of copper are the most insoluble said properties of the oil. Thus, we have estabcompounds of the metal. The mercaptides by lished that there is a critical value for copper reason oi analogous structure exhibit similar concentration in the 011. above which deteriorasolubilities in water, .but are slightly more soluble tion will occur, and below which the oil will be in oils due to the organic nature of the alkyl or stable as regards gum and color formation in aryl group presentin the mercaptide molecule. storage. The sulfides of copper have a solubility oi. about This improved process of stabilization depends 0.00033 gram per liter of water and an infinitesion the eilective removal of traces of copper commal solubility in hydrocarbon oils; the solubility pounds from the contaminated hydrocarbon oil of copper methyl mercaptide is approximately by treating said oil to completely: convert the 0.000003 gram per liter of cracked naphtha, or hydrocarbon oil-soluble copper compounds into about one-hundredth the solubility of copper sulcompounds whose solubility is less than the soluflde in water. These solubility figures are based bility of the copper salt of ethyl mercaptan. By on extremely sensitive colorimetric tests, especialthis means, and the subsequent separation of ly devised to indicate the presence and concenthese more insoluble compounds from the hydrotration of copper in hydrocarbon oil. carbon oil, the deterioration due to dissolved The following table shows the approximate copper compounds in the oil is prevented. solubilities of copper salts in oils, or the extent to Since the deterioration of oil is accelerated which oils-soluble copper compounds are formed in a catalytic manner by dissolved copper salts, by contact of the oils with said copper salts for a it follows that copper salts more insoluble than 24 hour period.

' Table I Copper salt Hydrocarbon oil w 332M Al hum Gram pg 1 ,000 06. Copper oxide Basi s-sweet cracked naphilnrter anL 0.0003 approx.) carbons c gfififiih m g g3 8.3% $5822.; 083523319 KER-'fliIIIZIIIIIII :::::c8:::::::::::::::::::::::: 311% 388% Copper silicat 60---. 0.0003 gapproxg C0999! 811mm r n 0.0003 approx.) Copper-n-butyl-mercaptide --c 0 0.0000 (approx.) Copper-t-butyl-mereaptide ..c o 0.300 'Copper-ethyl-mermptide r n 0.0mm

I 1 Sp. gr. 0! naphtha taken as 0.75. copper ethyl mercaptide are inactive as catalysts It will be seen from the values listed in Table I for deteriorative reactions in oil, and likewise that complete removal 01 copper from an oil may possess marked resistance to oxidation processes not be accomplished by contacting said oil with which would change said insoluble copper coma reagent to form any of the copper salts listed. pounds to more active forms which would be This fact is based on experimental data which injurious to the oil. proves that the deterioration of an 01-! due to Oil-soluble copper compounds which may be dissolved copper is not prevented unless the copiormedin complex hydrocarbon oil mixtures, parper content of said oil is reduced to a value less ticularly in petroleum distillates. are usually than 0.1 p. p. m. as shown in Table II. mercaptides or salts of acidic components such as 5 T bl H cresylic and naphthenic acids. Such compounds a e may be more soluble than copper ethyl mercap- C l tide, and likewise may not be removed, from an on oor A mm 011 in which said compounds are dissolved unless Hydlmm" 52293? 11115 2 the method of treating or stabilization forms use mm therewith copper compounds less soluble than copper ethyl mercaptide. For example, after a 21 cracked naphtha has been in contact with c pper West Texas crack- 10 +25 -16 Dark brown. oxide, copper carbonate or copper phosphate, 1 +25 Do sensitive tests show the presence of traces of cop- "I oYiIIIIIIIIIII +25 +12 -1a (301 01. per remaining in the naphtha, whereas a portion m i2 of the same naphtha after prolonged contact with dmso eg fiiefi so t iis m ira es-7122 3 21? Thus in order to prevent the deterioration of a amounts of copper salts present in a cracked hydrocarbon on which has been treated with a gasoline which has been sweetened with a cum-1c copper-containing reagent, it is necessary to treat chloride solution mayberemovedby adding t said oil in order to reduce the amount of dissolved to a controlled amount of methyl mercaptan to pp to 8 1 1658 than P- D- s 18 convert the more soluble copper compounds into accomplished according to our invention by contheless soluble copper methyl mercaptide. Comverting the copper present in the oil into compounds with oil solubility less than the oil-solu bility of copper-ethyl mercaptide.

As examples of the practice of my invention. the following examples are described:

EXAMPLE I A sample of cracked gasoline which had been sweetened by treatment with a solution containing cupric chloride was separated from the copper reagent and divided into two parts. One part was stored without further treatment. To the the original gasoline saturatedwith copper ethyl mercaptide. The tabulation of results is given otherportion was added a solution of methyl below:

Table III r a r No. Gasoline sample Copper test as): Zt og 30 days, go storage 1 Crackedgasoline-no additional treatment Negative +24 +22 +21 2 Cracked gasoline saturated with solid copper. ethyl Positive, approx. +24 +16 10 merca tide. 0.1 p. p. m.

3 #2 samp e-added 0.006percent methylmercaptan followed by Negative,less than +24 +22 +21 water wash. 0.1 p. p. m.

4 r #2 sample-plus 2 percent sour vapor recovery gasoline condo +24 +21 taining 0.01 percent methyl mercaptan.

5 :#2 'sampleintimately contacted with alkaline aqueous soludo +24 +22 +21 tion of dithizone.

6 #2 sample-contacted with ammoniacal solution 0! alphado +24 +22 +21 benzoinoxime.

7 #2 sample-contacted with aqueous solution oi thionalide d0 +24 +22 +21 8 #2 sa(: iple %ted with aqueous solution oi 5.7-dibromodo +24 +22 +21 9 #2 sample-contacted with ammoniacal solution or diethyldo +24 +22 +21 dithiocarbonate.

.nercaptan in sulfur-free hexane solution, the quantity added being suflicient to cause the gasoline to have a methyl mercaptan content of 0.003 weight per cent. After the addition of the mercaptan, the gasoline was allowed to stand for two hours, after which it was washed with water and stored. The results of this stabilizing treatment are shown below: V

the critical value for allowable copper concentration in oil which is stable with regard to color and gum formation in storage is thus disclosed.

i 1 or A rte a a or ppearance a r Gasoline samples Copper test 0010. "lays, days, storage storage Cracked gasoline unstabilized Positive, greater th n 1 p. p. m +24 -16 Dark brown, gummy. Cracked gasoline plus 0.003 percent Negative, less than 0.1 p. p. m +24 +23 +22 color.

methyl mercnptan.

1 This gasoline was doctor sweet; no trace of mercaptan after two days.

Eximrnn II We claim:

A sample of the same gasoline described in Example I was similarly treated except that the stabilizing reaction was brought about by the addition to one portion of the gasoline of sufflcient sour vapor recovery gasoline to amount to 2 per cent by volume. This vapor recovery gasoline contained approximately .01 weight per cent of methyl mercaptan. The results of this stabiliza- 1. In the process of sweetening hydrocarbon oil with copper reagents, the step of stabilizing the sweetened oil to prevent deterioration due to retained oil soluble copper salts which comprises adding a small quantity of a stabilizing agent comprising diethyldithiocarbonate.

2. The process as in claim 1 in which the stabilizing agent is an ammoniacal solution of dition are illustrated below: ethyldlthlooarbonate- Orig- Appearance Gasoline sample Copper test inal 55 after 30 color storage days storage Cracked gasoline-copper treatednnstabilized. Positive, greater than 0.1 p. p. m. +24 16 Dark brown. Cracked gasoline-copper treatedplps 2 percent Negative, less than 0.1 p. p. m +24 +23 +fl color.

(vol.) 0! sour vapor recovery gasoline.

1 This gasoline was doctor sweet.

Exmnn 111 To a sample of doctor sweet cracked gasoline was added solid copper ethyl mercaptide and WALTER A. SCHULZE. GRAHAM n. SHORT. 

